Airfoils constructed with cavities and passageways for carrying cooling fluid therethrough are well known in the art. For example, it is common to construct airfoils with spanwise cavities within the wider forward portion. These cavities often have inserts disposed therein which define compartments and the like within the cavities. The cooling fluid is brought into the cavities and compartments and some of the fluid is often ejected therefrom via holes in the airfoil walls to film cool the external surface of the airfoil. The trailing edge region of airfoils is generally more difficult to cool than other portions of the airfoil because the cooling air is hot when it arrives at the trailing edge since it has been used to cool other portions of the airfoil, and the relative thinness of the trailing edge region limits the rate at which cooling fluid can be passed through that region.
A common technique for cooling the trailing edge region is to pass cooling fluid from the larger cavity in the forward portion of the airfoil through the trailing edge region of the airfoil via a plurality of smaller diameter drilled passageways. Such an airfoil construction is shown in U.S. Pat. No. 4,183,716. Another common technique for convectively cooling the trailing edge region is by forming a narrow slot between the walls in the trailing edge region and having the slot communicate with a cavity in the forward portion of the airfoil and with outlet means along the trailing edge of the airfoil. The slot carries the cooling fluid from the cavity to the outlets in the trailing edge. An array of pedestals extending across the slot from the pressure to the suction side wall are typically incorporated to create turbulence in the cooling air flow as it passes through the slot and to increase the convective cooling surface area of the airfoil. The rate of heat transfer is thereby increased, and the rate of cooling fluid flow required to be passed through the trailing edge region may be reduced. U.S. Pat. Nos. 3,628,885; 3,819,295; and 3,994,622 are examples of airfoils constructed in this manner.
Another airfoil constructed with improved means for carrying cooling fluid from a cavity in the forward portion of the airfoil through the trailing region and out the trailing edge of the airfoil is shown in commonly owned U.S. Pat. No. 4,203,706. In that patent wavy criss-crossing grooves in opposing side walls of the trailing edge region provide tortuous paths for the cooling fluid through the trailing edge region and thereby improve heat transfer rates.
Despite the variety of trailing edge region cooling configurations described in the prior art, further improvement is always desirable in order to allow the use of higher operating temperatures, less exotic materials, and reduced cooling air flow rates through the airfoils, as well as to minimize manufacturing costs.